We are now embarking on an underground tour of JEWEL CAVE, located in Custer in the Black Hills.

At 140 miles, Jewel Cave is the second longest cave in the world. It is filled with calcite crystals and other wonders that make up the "jewels" of Jewel Cave National Monument. The cave's current length is: 140.80 miles.
The primary resource of Jewel Cave National Monument is the cave itself. Jewel Cave is a unique world of sparkling calcite crystals, delicate strands of gypsum, and other spectacular cave formations. It contains large rooms strewn with boulders, tight crawlways, and dark fissures leading into the unknown. The elevational range within Jewel Cave spans 631 feet. This is its official "depth." The highest point in the cave is 5,406 feet above sea level, and the lowest point is at 4,775 feet. The cave's depth below the surface varies a great deal. The cave intersects the surface in Hell Canyon, at the only natural entrance. The deepest point in the cave is 749 feet below ground.
Recent exploration trips have focused on the southeastern area of the cave, where many "leads" (unexplored passages) and strong airflow exist. Airflow within the cave is the single best indicator that large areas of the cave have yet to be discovered. Due to changes in barometric pressure, strong winds blow through Jewel Cave's passages miles from the natural entrance.